Stephen P. Wnuk

Glenn Research Center, Cleveland, Ohio

Son Le

Stennis Space Center, Stennis Space Center, Mississippi

Raymond A. Loew

Sierra Lobo, Inc., Fremont, Ohio

Evaluation of Data-Logging Transducer to Passively 

Collect Pressure Vessel p/T History

NASA/TM—2013-217852

March 2013
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Stephen P. Wnuk

Glenn Research Center, Cleveland, Ohio

Son Le

Stennis Space Center, Stennis Space Center, Mississippi

Raymond A. Loew

Sierra Lobo, Inc., Fremont, Ohio

Evaluation of Data-Logging Transducer to Passively 

Collect Pressure Vessel p/T History

NASA/TM—2013-217852

March 2013

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

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Acknowledgments

The authors would like to acknowledge support of Rocket Propulsion Test (RPT) Program Offi ce. RPT was an ideal sponsor in 

this venture. We would also like to thank the Aero-Acoustic Propulsion Laboratory (AAPL) test staff for their support in deploying 

the data-logging transducer within their Glenn Research Center (GRC) test facility and for covering this activity in spite of a

demanding and busy facility test schedule. We also acknowledge the efforts of Stennis Space Center (SSC) installation staff/crew, 

the technical advocacy of Haynes Haselmaier, the facilitation of Virgil Smith, and the leadership of Cliff Arnold.

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NASA/TM—2013-217852 1 

Evaluation of Data-Logging Transducer to Passively Collect 

Pressure Vessel p/T History 

Stephen P. Wnuk 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Son Le 

National Aeronautics and Space Administration 

Stennis Space Center 

Stennis Space Center, Mississippi 39529 

Raymond A. Loew 

Sierra Lobo, Inc. 

Fremont, Ohio 43420 

Abstract 

Pressure vessels owned and operated by NASA are required to be regularly certified per agency 

policy. Certification requires an assessment of damage mechanisms and an estimation of vessel remaining 

life. Since detail service histories are not typically available for most pressure vessels, a conservative 

estimate of vessel pressure/temperature excursions is typically used in assessing fatigue life. This paper 

details trial use of a data-logging transducer to passively obtain actual pressure and temperature service 

histories of pressure vessels. The approach was found to have some potential for cost savings and other 

benefits in certain cases. 

Introduction 

NASA has a long history of safe pressure vessel operation that is largely attributable to a rigorous 

vessel certification program. Vessel certification entails inspection and analysis to assess the effect and 

state of damage mechanisms such as corrosion and fatigue. While damage due to corrosion is readily 

assessable through standard Nondestructive Evaluation (NDE) inspection techniques, the state of vessel 

fatigue is not readily apparent and must be inferred from vessel service history. Historically, most field 

vessel applications are not easily monitored. Thus the service histories of such vessels are typically 

estimated based on operations logs, standard operating schedules, and the like. Since some of this 

evidence can be anecdotal in nature, safety factors are often applied to assure that the estimate errs 

conservatively high of actual pressure excursions experienced by the vessel. While conservative and safe, 

this practice produces a shorter vessel certification life than if the fatigue assessments were based on 

actual pressure excursions experienced by the vessel. This ultimately results in a shorter vessel service 

life, or more expensive analysis/inspection than would have been necessary if the actual service history of 

the vessel were known. With the advent of modern data logging transducers it is conceptually feasible to 

collect actual service histories of field vessels and realize considerable benefits through assessing vessel 

fatigue condition based on actual data. Seeking to exploit this development to operational gain, the 

Rocket Propulsion Test Management Board (RPTMB) commissioned a trial of two data logging 

transducers to evaluate their effectiveness in monitoring pressure and temperature excursions of vessels 

under widely diverse conditions. Final test applications included a low-pressure liquid nitrogen Dewar in 

southern US climate, and a high-pressure/high-volume gaseous nitrogen vessel in northern US climate. 

These two cases provide a considerable variety of vessel service conditions (pressure and temperature), 

vessel commodity, and environmental conditions. 
NASA/TM—2013-217852 2 

Nomenclature 

AAPL Aero-Acoustic Propulsion Laboratory 

NDE Nondestructive Evaluation 

P Pressure (psig) 

RPT Rocket Propulsion Test (NASA Program Office) 

RPTMB Rocket Propulsion Test Management Board 

T Temperature 

Hardware and Installation 

The transducer selected for trial was a MadgeTech Model PRTEMP1000IS. An image of the device is 

shown in Figure 1. This device has desirable features and characteristics including intrinsic safety, 

compact packaging, ambient temperature range, flexible sampling parameters, versatile software, and PC 

interface capability. Manufacturer specification literature is reproduced at the end of this report. 

The northern trial site was high pressure gaseous nitrogen vessel located on the NASA Glenn 

Research Center (GRC) campus in Cleveland, Ohio. The test vessel had an internal volume of 311 ft3

 and 

an operating pressure range of 1500 to 2200 psig. The site experiences moderate continental climate with 

summer highs reaching into the lower 90s (F) and winter lows dipping into the lower teens. Winter 

extremes of –20 occur on an average of once a decade. The transducer was plumbed directly into the 

vessel pressure sense line in parallel with the primary pressure display gauge and was mounted on the 

same indicator panel as the gauge. Views of the installation are shown in Figure 2. The transducer was 

unprotected from the elements and successfully endured over two-years of service with no problems or 

loss of function. 

Figure 1.—MadgeTech PRTemp1000IS intrinsically safe pressure and temperature data logger. 

 
NASA/TM—2013-217852 3 

Figure 2.—Views of data logging transducer installation at Glenn Research Center, Cleveland, Ohio. Clockwise from 

top left: End view of the vessel and pressure indicating panel, close up of transducer mounting, profile view of 

vessel (only half of vessel is seen in this view). 

 
NASA/TM—2013-217852 4 

Figure 3.—View of data logging transducer installed on 28,000 gal Dewar at Stennis Space 

Center (SSC), Mississippi (only end of vessel is seen in this view). 

The southern trial site was a 28,000 gal liquid Nitrogen Dewar located at Stennis Space Center (SSC) 

near the Mississippi state coast. The test Dewar was in service providing LN to the E-Complex Test 

Facility. This vessel has been used in several tests related to the Taurus project but not while the data 

tracker has been mounted. The vessel is pressurized to satisfy test requirement then it is depressurized. A 

view of the installation is shown in Figure 3. 

Results 

At GRC a high range transducer (0 to 5000 psig) was received, initiated, and installed without 

significant problem. There were some software compatibility and PC Operating System issues that had to 

be resolved with factory assistance, yet in retrospect these device setup issues were minor. Mounting and 

connection of the transducer into the vessel pressure sense panel was accomplished with very little effort 

in roughly an hour. The device was set to collect data at the default rate of once every 30-min (48 points 

per day). The transducer began service directly monitoring vessel gaseous nitrogen pressure in September 

2010. An initial data download was successfully acquired in January 2011. This initial 4-month data set is 

summarized in Figure 4. The transducer remained in service for two more years until January 2013. A 

download of the data acquired at that time indicated that transducer memory had reached full capacity in 

August 2011, and that no subsequent data points were recorded by the transducer. Due to unfamiliarity 

with the device, technicians had not known to reset the buffer. There was no visual indication that the 

device was at full capacity. The test trial was terminated at this time and the transducer was retired from 

the trial as well. Over its two year trial period the device easily tolerated climate extremes (rain, snow, 

and sleet) without any special protection. The initial battery also lasted the entire two year period, which 

is twice the advertised limit. 
NASA/TM—2013-217852 5 

p/T Pilot Data From GN2 Vessel at GRC Site

Figure 4.—Information collected by data logging transducer at GRC site over the period September 

2010 to January 2011. Vessel pressure data is shown in red (square icons, scale on left). Note 

zero pressure points at start and end of interval are due to transducer being removed for 

inspection at end of initial period. Vessel temperature data is shown in blue (diamond icons, scale 

on right). Temperature data captures summer highs in the 90s (F.) and winter lows in the teens. 

Every known pressure excursion of the vessel was accurately captured in the detail data. 

At the SSC site a low range transducer (0 to 100 psig) was likewise received, initiated, and installed 

without significant problem. A challenge was inherent in the installed location for this transducer, since 

contact with the cryogen would damage the transducer. The installed location is shown pictorially in 

Figure 3 and schematically in Figure 5. The transducer was installed on a 1/4 in. pressure sense line that 

measures the static head pressure at the bottom of the Dewar. The Dewar’s vent line is normally open to 

facilitate boil-off. The transducer was first activated around December 27, 2010. As with GRC, some 

factory assistance was required to resolve initial setup problems, and the transducer was set to collect data at 

a rate of once every 15-min. At the end of the first week (around January 3, 2011), staff pulled a sample to 

see if it was capturing data. It had in fact been capturing data however; the data did not make sense. The 

pressure and temperature readings were inverse to one another. As the temperature would rise the pressure 

would drop (relatively proportional amounts, degrees to pounds in both directions). This outcome was 

unexpected. The memory was cleared and the transducer was reinstalled in February 2011. The transducer 

was removed in October 2011. The data is summarized in Figure 6. The data was reviewed with engineers 

from SSC Engineering & Test Directorate. It is determined that the temperature measurement does not 

reflect the skin temperature of the inner vessel. The recorded temperature shows a trend that is consistent 

with ambient condition throughout the day. Given that the vessel vent valve is normally opened and the 

transducer is measuring the static head pressure, it is reasonable to attribute the decrease in pressure due to a 

reduction in static head as the ambient temperature increases throughout the day. 
NASA/TM—2013-217852 6 

Figure 5.—The transducer was installed in parallel with PT-10A42-LN. 

p/T Pilot Data From LN2 Dewar at SSC Site 

Figure 6.—Information collected by data logging transducer at SSC site from February to October 2011. 

Pressure data is shown in grey and temperature data is shown in red. Data indicate the transducer’s 

pressure sensing element became nonfunctional and the temperature sensing element was no longer 

accurate on May 5, 2011. The battery life was expended on July 29, 2011. 
NASA/TM—2013-217852 7 

Conclusions and Recommendations 

The set of trials described herein demonstrated the capability of data logging transducers to passively 

capture vessel service histories. Data acquired via these devices has potential to reduce vessel certification 

costs, improve safety, and extend the useful life of select vessels. Transducers could be used on a 

sampling basis to collect validation data underlying previous estimates. While not demonstrated in this 

trial, data from these devices could also be used to evaluate the actual severity of vessel pressure 

excursions. Such analysis may find, for example, that average pressure excursions for any particular 

vessel are much smaller (or larger) than previously thought, with obvious effects on assessed fatigue life. 

The devices could also be used to track rough or peak pressure excursions that might otherwise go 

undetected. The rugged and self-contained nature of these transducers makes them ideal for field or 

mobile applications where local power and control systems may not be readily available or reliable. 

These trails also demonstrated that deployment of data logging transducers is not quite as 

straightforward as previously imagined. Also, the devices have characteristics and limitations that make 

them unsuitable for some applications. For example, per unit purchase price with accessories can exceed 

$1000 (CY2010 data) which makes them uneconomical for widespread application to smaller vessels. 

Limited battery life and lack of visual health/status indicators could also frustrate some applications. The 

devices are not readily calibrated and are unsuitable for high precision test data collection. 

Recommendations for future application and study of data logging transducers include the following: 

 Application should involve vessels in the type of service where fatigue is a credible damage 

mechanism and where extending fatigue life can produce tangible savings. 

 Applications must involve service commodities that are compatible with the device. Cryogenic fluids, 

gaseous hydrogen, or highly reactive commodities may not be suitable for these transducers. 

 For any application, a formal monitoring program should be established and personnel should be 

specifically trained in use and operation of the transducers. These are not set and forget devices. They 

must be regularly checked and maintained. 

 Seek devices with some visual health/status indicators integral to the device. Having to plug into the 

device to determine low memory or low battery status can contribute to loss of data. Devices with 

wireless data transfer capability may be desirable in some applications. 

 These devices should be considered in circumstances where vessels are subject to potential out of 

tolerance conditions due to process control instabilities or such. They could provide an attractive 

monitoring alternative for capturing rogue excursion events. 
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14. ABSTRACT

Pressure vessels owned and operated by NASA are required to be regularly certified per agency policy. Certification requires an assessment 

of damage mechanisms and an estimation of vessel remaining life. Since detail service histories are not typically available for most pressure 

vessels, a conservative estimate of vessel pressure/temperature excursions is typically used in assessing fatigue life. This paper details trial 

use of a data-logging transducer to passively obtain actual pressure and temperature service histories of pressure vessels. The approach was 

found to have some potential for cost savings and other benefits in certain cases.

15. SUBJECT TERMS

Nondestructive evaluation (NDE); Transducer; Pressure vessel; Pressure temperature monitoring; Equipment health monitoring 

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